Purification of dicarboxylic acids



United States Patent PURIFICATION OF DICARBOXYLIC ACIDS Geraldine B. Corcoran, Chicago, 111., assignor to The C. P. Hall Co. of Illinois, Chicago, 111., a corporation of Ohio No Drawing. Application May 24, 1955 Serial No. 510,867

3 Claims. (Cl; 260-537) This invention relates to the purification of suberic acid contained in a crystalline mixture of carboxylic acids containing essentially suberic acid and azelaic acid.

Most commercial mixtures of suberic and azelaic acids contain a relatively small amount (e. g. 1 to 5 percent) of sebacic acid. This is illustrated in Table 1, below.

acids are designated herein as follows:

Suberic acid will be called C Azelaic acid will be called C and Sebacic acid will be called C the numbers indicating the number of carbons in the respective acids.

Such mixturesof acids are obtained bythe oxidation of saturated and unsaturated fatty acids from various sources, and particularly thedicarboxylic acid mixtures derived from tall oil fatty acids after removal of the rosin acids therefrom. They are also obtainable from saturated and unsaturated acyclic aliphatic hydrocarbons and oxygen derivatives thereof. They may be'obtained by oxidation of the foregoing by nitric acid, N0 N 04 or other oxides of nitrogen above N 0. Dicarboxylic acid mixtures obtained by such oxidations and containingrelatively high percentages of the lower dicarboxylic acids must first have the lower acids, such as the acids containing 4 to 7 carbon atoms, separated and removed there- These three higher molecular-weight dicarboxylic from to obtain mixtures containing only small amounts 1 of such acids before using the treatment covered herein.

Thus, such mixtures contain over 60 percent and as much as 90 to substantially 100 percent of the C C and C acids.

When crude dicarboxylic acids are produced from such sources they may have a composition as 'follows, depend ing upon the source of the starting materials. Table 1 shows the composition of dicarboxylic acids produced from acidulated cottonseed footsfatty acids (C. S. Foots F; A.) and from tall oilfatty acids :(Tall Oil F. A.) low in rosin acids.

TABLE 1 From Carbon No. Acid S. From Tall Fonts Oil F. A.

Percent c gm-maoioqga moat-nature E ooqcmoaoce The shorter chain acids may be separated from the C ,.C and C by dissolving such mixtures in a solvent such as orthodichlorobenzene, as more particularly described nad claimed in Pooler application Serial No. 169,542, filed June 21, 1950, now U. S. 2,7l6,133. Such recrystallized C C and C acids contain small amounts of the shorter chain dicarboxylic acids and particularly succinic and adipic acids, together with a small amount of monocarboxylic acids.

Study of the solubility of C C and C in nitric acid of 25, 40and 58 percent concentrations by weight at 25, 50, 80 and 90 C.-actually gave the following results for the solubility of dicarboxylic acids. (In the table, all solubilities are recorded as grams of dicarboxylic acid per liter.)

TABLE 2 Solubillties 25%HNO3 40% HNO; 58% HNOa Suheric Acid:

Temperature- 25 C i 0. 35 0.02 0. 06 C 1. 96 3. 94 24. 59 C- 52. 86 221. 77 398. 60 C 239. 44 651. 46 851. 22 Azelaic Acid: i V p Temperature- 25 C 0.07 0. 26 39.38 1 12; 02 21. 54 7 138.16 565. 47 1,463.69 1, 998. 89 90 C.: r. l, 419. 01 2, 378. 76 2, 636. 27 Sebaclc Acid:

Temperature solubility. in nitric: acid.

d third Percent and combining two The last The other figures in the fol- 57.6 percent of the starting Example 1a Total (The analyses of Tables 3 and 4 were made chromatographically. The weights are given in grams The fifth column shows, that the second an readily located in Table 3:

Succinic Glutarir Adipic Pimelic Suberic Azelaic Sebacic Monocarboxylic Thus, by one solution in nitric acid cuts taken at 60 and 54 material was recovered and in it the suberic acid content was raised from 67.50 percent (in the starting material,

The second and third cuts (Example 1), totaling 57.6

of each was recorded, together with the analysis of the remaining filtrate, and the analysis of the wash water.

5 figure in the fourth column refers to the 50.5 grams of starting material.

fractions (obtained by cooling to 60 and then 54 C.) total 57.60 percent of the starting material. The last column shows there is 1.12 percent of the lower molecular weight acids present. lowing analysis of the total of these two fractions, are

Acid:

30 above) to 81.55 percent.

Percent (by weight) t 4 11 25 n T I MMMRo uAA. 5 .W-.%M% 0 ww% m 2 2222222 as m m LLLLLLL u e n m u h. P 0 D u C m .48281155 0 d 04 6864 59 t d u .0 .57512336 5 n 255779304. A C W 17 111.11 m 5 20060512 0 0L1L1 1 mm mm trlat a .m P m M n .44463 5 F o -04\ 278l4 9 .D .m at .59 1850003 6 w i W "10110000 1 tv "35000000 000000 00 L n 65053305 G t e 0 .21399997 F n 56424308 V W "88766666 .E 6 07651 Di h m ZZZZZLUQL .w a T n u m fimmwflcwflmmw t U 07047672 771762 7 e m T009555M3 m C W U H U NJ 3600 24 m H 43222222 A m 2233a u33 G m P 0 .1 u M M m e 368405809 M b fl fimnflwnfl 2 .w W M w m m 02692508 1 w. H. tmzadurt M m M u b r M m F 0 830857828 0 h 1411 3 20 04 M m T m 588355$ t M F n 573287882 P .E 257298392 h H m4220l001 0 "10550050 T P n 16113079 9 e 910 4 45 9000000 W m m 12%2M22 7689885m M P n f 7 10 7 nv 9m0 m 5788890 n n. 1 m nawwmmnmn I 98738499. um d C m 712307160 .1 c e c 037 1 m m fiWWWMWNW A W wmnlah lean 4 5 7 0 H m 23%4445 m 5 4 1124 0 C N d Om- 94 1 9 M 8 Z H .L 9954559 9 M 02430001. 3 B N 0 0 l h m T 0 011104126 w 018833401 h 0 0mLeuZ7 m0 L T 1 1543334 P Example 1 (17.5% HNO In this example, 50.5 grams of mixed acids were used. The starting material contained 2.37 percent of mono- The increase in the purity of the suberic acid is marked when the crystalline starting material contains a large The following examples illustrate the invention by referring to crystallizations with 17.5 percent and 5 8 percent nitric acid.

Succinic Glutaric Adipic Pimelic Suberic Azelaic Sebacic- Monocarboxylic Total 1 By difference. V ,Fifty and one-half grams of this mixture were dissolved in 200 ml. of 17.5 percent HNO -by heating to Then as it was'cooled, variousfractions ofrcrystals were collected at the temperatures recordedin the second column of Table 3.

Cut No.

amount of azelaic acid since the nitric acid dissolves the azelaic acid in preference to the suberic and sebacic acids, as shown by the solubilities in Table 2. Little improvement is noted when there is no more than a small amount of azelaic acid in the mixture.

carboxylic acid. On the basis of the dicarboxylic acids present, this sample had the following analysis:

Acid:

Cut No.

Wash water percent of thestarting material, were subjected to further v fractional crystallization using further 17.5 percent HNOQ' table. Seven fractions were collected, and the analysis The results are given in Table 4. r

just under C. and came that Note No. 1: First crystals weighing a few milligramswere removed for chromatographic analysis.

7 The crystals began to form out over a wide range of temperatures as shown in cent of crystals at this temperature, having the following A marked reduction in'monocarboxylic acid and sebacic acid was noted as'a result of the treatment with non-polar solvent. j

A plant batch was similarly prepared from the above 95.07 percent suberic acid using orthodichlorobenzene. The plant equipment did not" permit the making of a filtration at 92 C. because of the open-top equipment employed. It was necessary to cool to room temperature. The crystals were taken up in water and hot filtered to remove the orthodichlorobenzene and any solid impurities. H The filtered solution"wascrystallized and the mother liquor removed. The crystalline product had the following analysis.

' By ditterence.

Nitric acid of different concentrations may be used,

' and difierent'temperatures may be employed." The fore going examplesare merely illustrative. The following claims define the invention.

WhatI claim is: 1 1. The process of purifying the suberic acid in a crystalline mass composed'essentially of suberic and azelaic acids, which comprises dissolving the mass in nitric acid of at least 15 percent concentration at a temperature of at least 70 C. and then, by cooling, obtaining a concentrated solution andjthen on further cooling to a temperature not below 35 C. cry'stallizing the suberic acid there from while retaining a substantial amount of a the azelaic acid dissolved in the nitric acid. p

2. The process of claim 1 in which the crystalline product is recrystallized from nitric acid.

3. The process of claim 1 in which the concentrated solution is cooled until at least substantially 80 percent of the suberic acid content thereof is crystallized out.

References Cited in the file of this patent I UNITED STATES. PATENTS 2,203,680 Ellingboe June 11, 1940 2,323,061 Lehmann et al. June 29, 1943 Pooler Aug. 23, 1955 

1. THE PROCESS OF PURIFYING THE SUBERIC ACID IN A CRYSTALLINE MASS COMPOSED ESSENTIALLY OF SUBERIC AND AZELAIC ACIDS, WHICH COMPRISES DISSOLVING THE MASS IN NITRIC ACID OF AT LEAST 15 PERCENT CONCENTRATION AT A TEMPERATURE OF AT LEAST 70*C AND THEN, BY COOLING, OBTAINING A CONCENTRATED SOLUTION AND THEN ON FURTHER COOLING TO A TEMPERATURE NOT BELOW 35*C., CRYSTALLIZING THE SUBERIC ACID THERE FROM WHILE RETAINING A SUBSTANTIAL AMOUNT OF THE AZELAIC ACID DISSOLVED IN THE NITRIC ACID. 